diff --git a/docs/SymptomsCausedByCOVIDLots/index.html b/docs/SymptomsCausedByCOVIDLots/index.html
index 0a876c8ce24..35a99d667a9 100644
--- a/docs/SymptomsCausedByCOVIDLots/index.html
+++ b/docs/SymptomsCausedByCOVIDLots/index.html
@@ -39,6 +39,7 @@
   <script src="./js/SymptomVsSymptomChartView.js"></script>
   <script src="./js/SymptomVsSymptomChartDataProvider.js"></script>
   <script src="./js/SymptomVsSymptomChartViewInitializer.js"></script>
+  <script src="./js/DictUtils.js"></script>
   <script>
     document.addEventListener(
       "DOMContentLoaded",
diff --git a/docs/SymptomsCausedByCOVIDLots/js/DictUtils.js b/docs/SymptomsCausedByCOVIDLots/js/DictUtils.js
new file mode 100644
index 00000000000..5af64ab2813
--- /dev/null
+++ b/docs/SymptomsCausedByCOVIDLots/js/DictUtils.js
@@ -0,0 +1,28 @@
+class DictUtils {
+
+    static retainCommonKeys({ dict1, dict2 }) {
+        const commonKeys = DictUtils.#getCommonKeys(dict1, dict2);
+        return {
+            dict1: DictUtils.#retainKeysOfDict(dict1, commonKeys),
+            dict2: DictUtils.#retainKeysOfDict(dict2, commonKeys)
+        };
+    }
+
+    static #getCommonKeys(dict1, dict2) {
+        return Sets.intersection(
+            DictUtils.#getKeySet(dict1),
+            DictUtils.#getKeySet(dict2));
+    }
+
+    static #getKeySet(dict) {
+        return new Set(Object.keys(dict));
+    }
+
+    static #retainKeysOfDict(dict, keys2Retain) {
+        const entries2Retain =
+            Object
+                .entries(dict)
+                .filter(([key, _]) => keys2Retain.has(key));
+        return Object.fromEntries(entries2Retain);
+    }
+}
\ No newline at end of file
diff --git a/docs/SymptomsCausedByCOVIDLots/js/SymptomVsSymptomChartDataProvider.js b/docs/SymptomsCausedByCOVIDLots/js/SymptomVsSymptomChartDataProvider.js
index 4168751077e..01b592a4457 100644
--- a/docs/SymptomsCausedByCOVIDLots/js/SymptomVsSymptomChartDataProvider.js
+++ b/docs/SymptomsCausedByCOVIDLots/js/SymptomVsSymptomChartDataProvider.js
@@ -1,17 +1,8 @@
 class SymptomVsSymptomChartDataProvider {
 
-    // FK-TODO: extract utility class and test
-    static retainCommonKeys({ dict1, dict2 }) {
-        const commonKeys = SymptomVsSymptomChartDataProvider.#getCommonKeys(dict1, dict2);
-        return {
-            dict1: SymptomVsSymptomChartDataProvider.#retainKeysOfDict(dict1, commonKeys),
-            dict2: SymptomVsSymptomChartDataProvider.#retainKeysOfDict(dict2, commonKeys)
-        };
-    }
-
     static getChartData({ prrByLotX, prrByLotY }) {
         const { dict1: prrByLotXCommon, dict2: prrByLotYCommon } =
-            SymptomVsSymptomChartDataProvider.retainCommonKeys(
+            DictUtils.retainCommonKeys(
                 {
                     dict1: prrByLotX,
                     dict2: prrByLotY
@@ -27,22 +18,4 @@ class SymptomVsSymptomChartDataProvider {
                     }))
         };
     }
-
-    static #getCommonKeys(dict1, dict2) {
-        return Sets.intersection(
-            SymptomVsSymptomChartDataProvider.#getKeySet(dict1),
-            SymptomVsSymptomChartDataProvider.#getKeySet(dict2));
-    }
-
-    static #getKeySet(dict) {
-        return new Set(Object.keys(dict));
-    }
-
-    static #retainKeysOfDict(dict, keys2Retain) {
-        const entries2Retain =
-            Object
-                .entries(dict)
-                .filter(([key, _]) => keys2Retain.has(key));
-        return Object.fromEntries(entries2Retain);
-    }
 }
\ No newline at end of file
diff --git a/docs/SymptomsCausedByCOVIDLots/test/DictUtilsTest.js b/docs/SymptomsCausedByCOVIDLots/test/DictUtilsTest.js
new file mode 100644
index 00000000000..d918bf065f1
--- /dev/null
+++ b/docs/SymptomsCausedByCOVIDLots/test/DictUtilsTest.js
@@ -0,0 +1,52 @@
+QUnit.module('DictUtilsTest', function () {
+
+    QUnit.test.each(
+        'shouldRetainCommonKeys',
+        [
+            [
+                {
+                    dict1: {
+                        "lotX": 1.0
+                    },
+                    dict2: {
+                        "lotY": 2.0
+                    }
+                },
+                {
+                    dict1: {
+                    },
+                    dict2: {
+                    }
+                }
+            ],
+            [
+                {
+                    dict1: {
+                        "lotX": 1.0,
+                        "lotCommon": 2.0
+                    },
+                    dict2: {
+                        "lotCommon": 3.0,
+                        "lotY": 4.0
+                    }
+                },
+                {
+                    dict1: {
+                        "lotCommon": 2.0
+                    },
+                    dict2: {
+                        "lotCommon": 3.0
+                    }
+                }
+            ]
+        ],
+        (assert, [dicts, dictsHavingCommonKeys]) => {
+            // Given
+
+            // When
+            const dictsHavingCommonKeysActual = DictUtils.retainCommonKeys(dicts);
+
+            // Then
+            assert.deepEqual(dictsHavingCommonKeysActual, dictsHavingCommonKeys);
+        });
+});
\ No newline at end of file
diff --git a/docs/SymptomsCausedByCOVIDLots/test/SymptomVsSymptomChartDataProviderTest.js b/docs/SymptomsCausedByCOVIDLots/test/SymptomVsSymptomChartDataProviderTest.js
index bada17d4c58..159e8248536 100644
--- a/docs/SymptomsCausedByCOVIDLots/test/SymptomVsSymptomChartDataProviderTest.js
+++ b/docs/SymptomsCausedByCOVIDLots/test/SymptomVsSymptomChartDataProviderTest.js
@@ -1,55 +1,5 @@
 QUnit.module('SymptomVsSymptomChartDataProviderTest', function () {
 
-    QUnit.test.each(
-        'shouldRetainCommonLots',
-        [
-            [
-                {
-                    dict1: {
-                        "lotX": 1.0
-                    },
-                    dict2: {
-                        "lotY": 2.0
-                    }
-                },
-                {
-                    dict1: {
-                    },
-                    dict2: {
-                    }
-                }
-            ],
-            [
-                {
-                    dict1: {
-                        "lotX": 1.0,
-                        "lotCommon": 2.0
-                    },
-                    dict2: {
-                        "lotCommon": 3.0,
-                        "lotY": 4.0
-                    }
-                },
-                {
-                    dict1: {
-                        "lotCommon": 2.0
-                    },
-                    dict2: {
-                        "lotCommon": 3.0
-                    }
-                }
-            ]
-        ],
-        (assert, [dicts, dictsHavingCommonKeys]) => {
-            // Given
-
-            // When
-            const dictsHavingCommonKeysActual = SymptomVsSymptomChartDataProvider.retainCommonKeys(dicts);
-
-            // Then
-            assert.deepEqual(dictsHavingCommonKeysActual, dictsHavingCommonKeys);
-        });
-
     QUnit.test('shouldProvideChartData', function (assert) {
         // Given
         const prrByLotX = {
diff --git a/docs/SymptomsCausedByCOVIDLots/test/index.test.html b/docs/SymptomsCausedByCOVIDLots/test/index.test.html
index 73ce91fb448..4b36a979259 100644
--- a/docs/SymptomsCausedByCOVIDLots/test/index.test.html
+++ b/docs/SymptomsCausedByCOVIDLots/test/index.test.html
@@ -19,6 +19,7 @@
     <script src="../js/SymptomVsSymptomChartView.js"></script>
     <script src="../js/SymptomVsSymptomChartDataProvider.js"></script>
     <script src="../js/SymptomVsSymptomChartViewInitializer.js"></script>
+    <script src="../js/DictUtils.js"></script>
     <link rel="stylesheet" href="https://code.jquery.com/qunit/qunit-2.17.2.css">
     <script src="https://code.jquery.com/qunit/qunit-2.17.2.js"></script>
     <script type="text/javascript" src="./jshamcrest.js"></script>
@@ -28,6 +29,7 @@
         JsMockito.Integration.QUnit();
     </script>
     <script src="./SymptomVsSymptomChartDataProviderTest.js"></script>
+    <script src="./DictUtilsTest.js"></script>
 </head>
 
 <body>